Wang Yibo, Hossain Md Sazzad, Li Tianlin, Xiong Yanwei, Le Cuong, Kuebler Jesse, Raghavan Nina, Fernandez-Ballester Lucia, Hong Xia, Sinitskii Alexander, Centurion Martin
Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA.
Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
Nat Commun. 2025 Aug 30;16(1):8132. doi: 10.1038/s41467-025-63533-9.
Two-dimensional ferroelectric materials like NbOI have garnered significant interest, yet their temporal response and synergetic interaction with light remain underexplored. Previous studies on the polarization of oxide ferroelectrics have relied on time-resolved optical second harmonic generation or ultrafast X-ray scattering. Here, we probe the laser-induced polarization dynamics of NbOI nanocrystals using ultrafast transmission electron diffraction and deflectometry. The deflection of the electron pulses is directly sensitive to the changes in the polarization, while the diffraction signal captures the structural evolution. Excited with a UV laser pulse, the polarization of NbOI is initially suppressed for two picoseconds, then it recovers and overshoots, leading to a transiently enhanced polarization persisting for over 200 ps. This recovery coincides with coherent acoustic phonon generation, triggering a piezoresponse in the NbOI nanocrystals. Our results offer a new method for sensing the ferroelectric order parameter on femtosecond time scales.
像铌氧碘（NbOI）这样的二维铁电材料已引起了广泛关注，但其时间响应以及与光的协同相互作用仍未得到充分研究。先前关于氧化物铁电体极化的研究依赖于时间分辨光学二次谐波产生或超快X射线散射。在此，我们使用超快透射电子衍射和偏转测量法来探测铌氧碘纳米晶体的激光诱导极化动力学。电子脉冲的偏转对极化变化直接敏感，而衍射信号则捕捉结构演变。用紫外激光脉冲激发后，铌氧碘的极化最初在两皮秒内受到抑制，然后恢复并超调，导致持续超过200皮秒的瞬态增强极化。这种恢复与相干声子的产生相吻合，从而在铌氧碘纳米晶体中引发压阻响应。我们的结果提供了一种在飞秒时间尺度上传感铁电序参量的新方法。
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